1. Technical Field
The present invention relates to a liquid crystal device having a plurality of pixels that each have a pixel switching element, a pixel electrode, and a storage capacitor. More particularly, the invention relates to a structure of a capacitor line for providing a storage capacitor.
2. Related Art
A typical technique for improving viewing angle characteristics of a liquid crystal device may be used to produce a vertical alignment (VA) mode liquid crystal device. A VA mode liquid crystal device uses a nematic liquid crystal material having a negative anisotropy of dielectric constant as a liquid crystal material and a vertical alignment film. For such a liquid crystal device, dividing a pixel electrode into a plurality of sub-pixel electrodes connected with a connecting portion therebetween in order to control an alignment of a liquid crystal has been proposed (See JP-A-2003-228073).
In such a VA mode liquid crystal device, when a storage capacitor is formed in parallel with a liquid crystal capacitor, a capacitor line 3b is formed in parallel with a scanning line 3a on an element substrate 10 as shown in FIGS. 6A and 6B. A storage capacitor 60 is formed by this capacitor line 3b, an extending portion 1x that extends from the drain region of a thin-film transistor 30 that constitutes a pixel switching element, and an insulating film formed simultaneously with a gate insulating layer 2. In order to realize a capacitance greater than or equal to a certain value for the storage capacitor 60, the capacitor line 3b must have a large width. As a result, an aperture ratio per pixel (a ratio of a region through which display light can be transmitted in a pixel region) decreases. In particular, a pixel electrode 7a is often divided into a plurality of sub-pixel electrodes 7b and 7c connected with a connecting portion 7e therebetween in such a VA mode liquid crystal device. In such a case, cutouts 7f provided between the sub-pixel electrodes 7b and 7c are domain regions in which an alignment of a liquid crystal cannot be controlled. Therefore, in such a VA mode liquid crystal device, providing a sufficient capacitance to the storage capacitor 60 leads to a disadvantage that the quality of a display image may be easily degraded; for example, sufficient amount of display light may not be able to be maintained.
Such a disadvantage exists not only for the VA mode liquid crystal device but also for, for example, an IPS (in-plane switching) mode liquid crystal device, in which a liquid crystal is driven by a horizontal electric field. That is, in such an IPS mode liquid crystal device, a pixel electrode or a common electrode is often formed in a bent pectinate shape in order to reduce changes in color caused by an angle of visibility. In such a case, a domain region that does not contribute to display is generated at a bent portion. Thus, in the IPS mode liquid crystal device, forming a storage capacitor having a sufficient capacitance also leads to a disadvantage that the quality of a display image may be easily degraded; for example, a sufficient amount of display light may not be able to be maintained.